In the prior art, various jigs or templates have been proposed to facilitate the attachment of locking devices for security purposes.
U.S. Pat. No. 5,116,170 to Palmer et al. discloses a door preparation drill jig useful to prepare a door to receive a door lock set. The jig has a cylindrical body which fits snugly into a main bore of a door. When mounted in the main door, mounting holes can be drilled using a drill bit and drill guides extending from the door preparation drill jig.
U.S. Pat. No. 5,114,285 to Brydon discloses a three-sided drilling template for a door. The drilling template includes a plurality of through guide holes located along sides thereof for marking the centers of mounting holes for mounting of hardware such as door locks and knobs.
U.S. Pat. No. 4,280,776 to Chaconas et al. discloses a drill guide for use during the installation of lock sets in doors. The drill guide has a body through which an aperture extends for drilling of pilot holes for lock set installation.
In the prior art, it is also known to install combination locks in doors using a combination lock deadbolt assembly which includes an automatic deadbolt holdback feature. An example of this type of a deadbolt assembly is a Lockmasters LM-5100, manufactured in Nicholasville, Ky.
Typically, these types of deadbolt assemblies are mounted on the inside surface of a door with a drill resistant hard plate mounted adjacent thereto. However, since the drill resistant plate is mounted to the deadbolt, openings drilled through the door must be accurately located to avoid installation difficulties.
The use of templates or other marking utensils has not provided an accurate way to install these types of deadbolt assemblies. When using a template to make a drilling hole, the drill bit may tilt or angle with respect to the door surface or holes formed using the template may not align with openings in the lock hardware.
In view of these deficiencies, a need has developed to provide an improved method for installing these types of deadbolt assemblies in conjunction with combination locks.
In response to this need, the present invention provides a method for installing combination lock deadbolt assemblies using a tapered drill guide which interfaces with tapered bores in the deadbolt assembly to accurately locate drilling holes for deadbolt installation.